111666171616561 has 2 divisors, whose sum is σ = 111666171616562. Its totient is φ = 111666171616560.

The previous prime is 111666171616523. The next prime is 111666171616583. The reversal of 111666171616561 is 165616171666111.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 109532655666225 + 2133515950336 = 10465785^2 + 1460656^2 .

It is an emirp because it is prime and its reverse (165616171666111) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 111666171616561 - 2²⁷ = 111666037398833 is a prime.

It is not a weakly prime, because it can be changed into another prime (111666171613561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 55833085808280 + 55833085808281.

It is an arithmetic number, because the mean of its divisors is an integer number (55833085808281).

Almost surely, 2^{111666171616561} is an apocalyptic number.

It is an amenable number.

111666171616561 is a deficient number, since it is larger than the sum of its proper divisors (1).

111666171616561 is an equidigital number, since it uses as much as digits as its factorization.

111666171616561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1632960, while the sum is 55.

The spelling of 111666171616561 in words is "one hundred eleven trillion, six hundred sixty-six billion, one hundred seventy-one million, six hundred sixteen thousand, five hundred sixty-one".